1. Field of the Invention
The present invention relates to an arithmetic processing device which carries out a calculation in accordance with a predetermined key operation and displays a calculation result, and which displays a specific mark when a key operation other than the predetermined key operation is carried out.
2. Description of the Related Art
Conventionally, an apparatus called a portable electronic calculator has been known which has a function of inputting numeric values and various operators. The electronic calculator calculates numeric values on the basis of an input operator, and displays the calculation result. Further, there are electronic calculators called scientific electronic calculators which can carry out, in addition to arithmetical operations, various functional calculus of trigonometric functions, logarithmic functions, and the like.
In such scientific electronic calculators, there are many types of available functions or functionalities (hereinafter, simply called functions for short), and on the other hand, the number of utilizable keys is limited as a compact electronics device. Then, all the functions cannot be allocated to dedicated keys, and a menu screen on which a list of functions is displayed as a menu, and the function is input by designating a numeric key allocated to a function on the menu, has been known (Japanese Patent Application KOKAI Publication No. 2001-166864).
However, in the menu display device described above, when a key which does not correspond to the menu (for example, a key other than predetermined numeric keys) is operated during a display of the menu, it is impossible to know whether the operated key is received as a valid instruction, or the operated key is not received as a valid instruction and handled as an invalid instruction. For example, in an electric calculator, when a user operates another key which does not correspond to the items of the menu in error in the process of inputting an arithmetic expression, the user loses sight to what extent the arithmetic expression has been input. Consequently, the user is required to input the arithmetic expression again from the beginning.